Embodiments described herein relate to engines of vehicles. More specifically, embodiments described herein relate to firing decks of engines for vehicles.
A cylinder block and a crankcase form the main structural component of an engine, and are often cast integral with each other. The crankcase forms the housing of a crankshaft, and the cylinder block defines at least one cylinder bore, within which combustion takes place to drive the crankshaft. The cylinder bore acts as a guide and as a sealing surface for a sliding piston and rings, and as such, the cylinder bore should be accurately machined to minimize out-of-roundness.
The cylinder block includes a firing deck at a top surface of the cylinder block. Head bolts, typically four for each cylinder bore, are introduced into bosses disposed through the firing deck to attach the cylinder block to a cylinder head.
Due to the uneven distributions of both cylinder block stiffness and clamping forces developed from the placement of the head bolts through the firing deck, the cylinder bores can undergo distortion. Mathematically, the bore distortion can be decomposed into many orders, and it is known that fourth order distortion of the cylinder bores can result in increased engine oil consumption. Additionally, the gasket sealing pressures are decreased at locations between the head bolts due to the structural weakness (less stiffness) there. The decreased gasket sealing pressures can in turn lead to combustion leaks and can also lead to engine failure.
To address the distortion in conventional crankcases, the firing deck has conventionally been reinforced by filling in shake-out holes that are located on the intake side only of the firing deck, or modifying the tooling for the casting to eliminate the shake-out holes. Further, the filled-in shake-out holes have been provided with arch-formations on a bottom or coolant side surface of the firing deck at the intake side only.
The firing deck of a conventional cylinder block typically has a uniform thickness, however to address distortion and to reinforce the firing deck, areas of increased thickness have sometimes been added to an exhaust side only of the firing deck. Further, the thickness of the firing deck between the cylinder bores (generally on a line connecting the centers of adjacent cylinder bores) has sometimes been increased up to fifty percent. However, bore distortions can continue to occur in the conventional cylinder block.